AT&T Att International data and call charges Dallas Texas

I have recently went for a trip a lost my sim. I have never used my sim, and its always out of my phone, as i have used local sim. I lost my sim and i raised a complaint as asked for a sim replacement, they failed to do that as i am out of country. So i thought of taking a new sim. When i reach back. To my surprise they charged me $400+ all together international data and calls. I spoke the representative, she spoke so sweet and handed over to In-charge or manager whatever, here name is Maria, she was so rude and argued that those are legit charges. If the charges are going over the limit atlest they should email us a warning or so... This is purely their negligence and made me to pay the whole amount. I am very much disappointed with this approach, we have account with them Since 8 yrs and this is the first time at least they should consider the coustmer loyalty. We have 8 connections on the same account, we all are planning to move out. Thanks for your hospitality At&t. All please avoid this company. It was good, now this company has changed.